This invention relates to a process for the production of a carbonyl compound by reaction of a carbonylatable compound such as an alcohol, a carboxylic acid ester, an ether or an olefin with carbon monoxide in the presence of a carbonylation catalyst containing a noble metal complex supported on a porous, crosslinked resin having pyridine nuclei.
It is known to produce a carbonyl compound by reaction of a carbonylatable compound such as an alcohol, a carboxylic acid ester, an ether or an olefin with carbon monoxide (CO) in the presence of a carbonylation catalyst containing a noble metal complex supported on a porous, crosslinked resin having pyridine nuclei. Examples of known processes of this class include the production of acetic acid by carbonylation of methanol, the production of acetic anhydride by carbonylation of methyl acetate and production of an aldehyde by hydroformylation of an olefin.
For example, U.S. Pat. No. 5,155,261 discloses a process for producing acetic acid by reacting methanol in a solvent with CO in the presence of an alkyl iodide and a solid catalyst containing rhodium complex supported on a porous, crosslinked vinyl pyridine resin (hereinafter referred to as VP resin). In such a process, there are obtained a liquid product containing acetic acid, unreacted methanol, methyl iodide, a solvent and by-products such as methyl acetate, propionic acid, water and hydrogen iodide, and a gaseous product containing an reacted CO, methyl iodide and by-products such as CO.sub.2, H.sub.2 and CH.sub.4.
The above process when applied to an industrially acceptable continuous mode generally includes a reaction step in which the carbonylatable compound is reacted with CO in the presence of the supported catalyst to produce a carbonyl compound, a separation step in which the liquid product is separated into the carbonyl compound and a residual liquid, and a recycling step in which the residual liquid is recycled into the reaction step. Such a process has been found to encounter the following problems.
First, a small amount of the noble metal is apt to be liberated from the solid catalyst and is transferred into the liquid product, so that the catalyst activity of the solid catalyst is reduced. Further, the liberated noble metal when introduced together with the liquid product into the separation step is apt to deposit onto the inside wall of the separation device such as a distillation tower and can no longer be recovered. The liberation of the noble metal from the solid catalyst also occurs when the porous VP resin is broken during the reaction step.
Another problem is that the reactor, the separator, etc. are apt be corroded because of the high corrosiveness of the liquid product. Thus, it is necessary to use a highly stable metal material such as zirconium or Hastelloy B. This causes increased apparatus costs.
A further problem is that by-products such as acetaldehyde and its derivatives including crotonaldehyde, 2-ethylcrotonaldehyde, ethanol, propionic acid, ethyl iodide, butyl iodide and hexyl iodide are produced so that the permanganate time of the carbonyl product is adversely affected and the iodine content thereof is increased.